US 2570170 A
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Oct. 2, 1951 J. G. M. vm
COMPOUND ESCAPEMENT WITH SPRING MOUNTED MASS Filed March 19, 1949 Fig. 4.
EFFECT/V5 FOHCE 0/? CURRA'NT RANGE APPZ /D FORGE OF? CURRENT Inverwtor: John G. MrVibi,
Patented Oct. 2, 1951 COMPOUND ESCAPEMENT WITH SPRING MOUNTED MASS John G. M. Viti, Philadelphia, Pa., assignor to General Electric Company, a corporation of New York Application March 19, 1949, Serial No. 82,468
-My invention relates to an improvement in escapement mechanisms, and more particularly to an escapement device used for producing a variable retarding effect. The invention may be utilized especially in connection with a delayedaction circuit breaker and provides a time delay which is more variable in accordance with the degree of overcurrent passing through the breaker than is the case with conventional escapement mechanisms.
The use of escapement devices to regulate or retard motion is well known. The anchor type of escapement is particularly well known.
The conventional anchor escapement is comprised of a centrally-pivoted body or pallet having projections at each end which engage the teeth of an adjacent ratchet or escapement Wheel. As the escapement wheel rotates, the pallet oscillates about its pivot as its end projections mesh into and out of the ratchet teeth. Due to its engagement with the oscillating pallet, a retarding action is produced on the escapement wheel, the degree of retardation being a function of the inertia of the pallet and that of any mass connected rigidly thereto.
A limitation of the conventional anchor escapement which may prove undesirable in certain applications is that with any given mass which the pallet member may have, the escape ment wheel will be restrained in accordance with what might be termed a natural force-time.
characteristic, the time or delay having an inverse relationship to the turning force or moment applied at the ratchet wheel. In cases where the applied force is always the same, the retard- L ing time or delaying action also will not vary. Such is the case, for example, in the conventional timer mechanism employed for regulating the reclosing delay of a circuit recloser as set forth in U. S. Patent 2,069,082 to Walle which is assigned to the same assignee as the present application. Where automatic circuit reclosers of this type are used, say, on a coordinated cascade rural distribution system, it is usual to employ pallet weights of different masses for reclosers of different current or interrupting capacity, those for the smaller ratings having heavier timer weights so that they operate with a longer reclosing time than the reclosers of higher amperage rating nearer to the power source. It will be clear, then, that increasing the effective pallet mass will increase the retarding effect or increase the time delay. Thus, if it were possible to vary the pallet mass automatically in accordance with the applied force, it will be apparent that a vari 1 Claim. (Cl. 74--1.5)
able force-time characteristic wouldbeobtained.
in contra-distinction to that of the natural one defined hereinbefore. In accordance with my invention, I achieve a variable force-time characteristic by articulate.
ing, with spring means, the mass of (or the mass associated with) the pallet of an escapement timer mechanism, as will be more clearly explained hereinafter.
When a timer mechanism is required to provide a time-delay opening for, say, a reclosing circuit breaker, it is desirable that the time-delay force-time characteristic be variable rather than natural; that is, the interrupting contacts preferably should open considerably faster for heavy overload currents than would be the case with a timer mechanism operating with a natural current-time characteristic.
This is particularly desirable when the power circuit which the recloser or breaker interrupts is provided with appropriate protective fuses, as
the time required for the fuses to open depends on the over-current magnitude, and therefore the time required for the breaker to open should also be related to the over-current magnitude,
instead of due to rare excessive overloads, as is the intended function of the fuse.
On the other hand, it often is desirable that the breaker open with at least some predetermined brief delay so that the fault is given an opportunity to clear itself. Because the currenttime characteristics of coordinated fuses in a cascaded system lie along a steeper plotted curve than the natural force-time characteristic of a conventional timer mechanism, it is desirable to provide a timer having an appropriate variable force-time characteristic.
It is, therefore, an object of my invention to 7 provide an escapement mechanism which will automatically modify its retarding effect to follow a variable force-time characteristic in accordance with the force available from the device being controlled.
It is a further object of my invention to provide.
9.21 escapement timer device which in effect operates with a variable inertia reaction in its response to externally applied forces.
It is a still further object of my invention to provide an escapement device which will variably retard the opening or closing of a circuit breaker, in accordance with predetermined requirements of some controlling condition, such as degree of over-current.
My invention will be better understood from the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claim.
In the drawings, Fig. 1 shows an escapement embodying my invention comprising an oscillating pallet with its associated spring-mounted mass, cooperating with an escapement wheel.
Fig. 2 shows an end view of the pallet, springmounted mass and escapement wheel of Fig. 1.
Fig. 3 shows the pallet and spring-mounted massof Fig. l as part of an operating mecha nism which provides a variable time delay opening for a circuit interrupter.
Fig. 4 is a graphic comparison between the time delays provided by the conventional escapement mechanisms and the escapement of this invention.
Referring now to the drawings, Fig. 1 shows an embodiment of the articulated-mass pallet of my invention, cooperating with an-escapement wheel. As will be seen from the drawing, the oscillating escapement assembly i consists of a light-weight pallet member 2 and a superposed mass 3, both pivotally mounted on the same pin -l, and having appropriate springs 5 disposed between the pallet and mass. Mass 3 is provided with two recesses 6 and 7 into which springs 5 are placed. When inserted therein, these springs extend beyond the recesses 6 and I so as to abut against the inside surfaces of pallet projections 8. projections 8 of pallet member 2 mesh with the teeth of escapement wheel 9.
As shown in Fig. 2, pallet member 2 has two sides H], II which are spaced apart a sufficient distance to permit mass 3 to fit between them with suitable working clearance. The sides II are connected to each other at their ends where the pallet teeth or projections 8 constitute a bridge across the space between the two sides.
When escapement wheel 9 is driven due to some comparatively low externallyapplied"mo ment, it will move so slowly as to'cause the entire pallet assembly I, consisting of pallet memher 2, mass 3' and interposed springs 5, to oscillate as a single unit about pivot Because the springs 5 are selected so as to have strength enough to overcome low inertia forces of the mass" 3, they will transmit the movement of the pallet 2 tothe mass 3 so that at slow speeds these'three elements, pallet, springs, and mass, will move together substantially in phase as a solid member.
If now a somewhat larger driving force is ap-- plied, the speed of rotation of escapement wheel 9"will increase and the oscillations of mass 3 will become less pronounced, due to the inability of the relatively light springs 5 to transmit enough force to preponderate over the inertia of the mass although pallet 2 will be oscill-ating'rapidly. In-
this extreme condition, it will be appreciated that It will thus be discerned that a 4 (neglecting the mass of the light springs 5) the retardation or delay effect will be due to that of the inertia of the pallet 2 alone, so that the mass 3 may be regarded as being virtually nonexistent.
Thus, the oscillatory characteristics of the escapement assembly I does not depend solely on one mass as doesthe conventional anchor escapement. Instead, the total mass may be split into plural parts, pallet 2 and mass 3, which acts as one mass at lower speeds, and as two masses at higher speeds, one of which, mass 3, becomes ineffective at higher speeds in so far as retardation effect is concerned. While I have shown the pallet mass articulated into two spring-connected components, it will be apparent that I can subdivide" it into a greater number of spring-connected plural mass components.
Fig. 3 shows schematically an application of the escapement device of this invention to a timedelay opening mechanism for a circuit breaker.-
Assuming that an overload exists on the circuit,-
an excess amount of current will pass through solenoid [2 which is in series with one of the power lines. This excess current will be sufficient to cause armature or core l3 to be pulled up into' the solenoid. However, the motion of the core will be delayed by means of the escapement device as follows: One end of the shaft or rod ['4' to which core [3 is attached is provided with ratchet teeth l5 which engage ratchet wheel l6.-
Due to the use ofescapement device I, the
speed with which rod I4 is permitted to move upwardly so as to open switch [9 varies greatly with the degree of overload on the circuit. On the other hand, if a conventional anchor type escapement were used, the amount of time delay before opening the circuit would not have nearly the flexibility provided with this invention.
The performance of my articulated mass palletmay be compared best with that of the former solid mass pallet escapement mechanisms by re-- ferring to Fig. 4 which graphically illustrates by curves the force-time characteristics involved.
The several curves are represented as commencing and terminating within the force or current range over which the respective escapements are effective. plot of the natural force-time characteristic of a conventional escapement employing a relatively heavy mass fixed to the pallet. If a light mass pallet be substituted for a heavy mass pallet the resulting plot would produce a curve similarto the first but lying generally at a lower level (shorter time) as represented by the dotted curve I Assuming now that the desired force-time" characteristic of the fuses with which it is desired to coordinate the breaker lie along a steeper plot,
say, from A to b, Ican fulfill this requirement by the proper selectionof pallet weight, springstrength, and weight'of the-superposed mass. To'
this end, ifthepallet'weight is made equal The dotted curve AB is a mass to the light-weight pallet mass which produces the curve ab, and an articulated springconnected mass is applied thereto such that the summation of the mass and pallet is the equivalent of that of the heavy solid-mass pallet which produced curve AB, then, in accordance with the explanation already set forth, it will be understood that a plot of the resulting variable force-time characteristic curve will conform somewhat to the full line curve Ab on the diagram. In other words, and as borne out by tests on samples of my device, the variable force-time characteristic of the articulated mass pallet will generally conform at one end of its range to that of the heavy mass pallet curve AB, and will also generally conform to that of the light-Weight mass at the other end of the range as at b. Intervening points between A and b on this curve will follow a plot representation which will conform more or less to the gradual transition repesented by the full line curve Ab having the desired steeper slope which is unattainable through the agency of the former fixed. mass pallet design.
From the above explanation, it will be perceived that I can achieve even greater variability by employing a still heavier combined spring connected mass, in which case the full line curve would commence at some point higher than A; and if the pallet mass alone were made correspondingly lighter, the right hand end of the curve would then lie at some point lower than that indicated by b. If the total mass i subdivided into more than two spring-divided articulated elements, it is expected that the path or transition from the higher end to the lower of the effective range Ab would follow a more uniform or predictable pattern.
Thus it will be seen that I have provided means for producing a "variable force-time characteristic which more nearly conforms to that of a series of cascaded protective fuses than has been possible hitherto by means of the fixedmass conventional escapement devices of the prior art.
While there have been shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claim to cover all such changes and modifications as fall within the true spirit and scope of the invention.
What I claim as new and desire to secure by Letters Patent of the United States is:
A time delay means comprising a toothed escape wheel, a centrally pivoted pallet member having projections at its opposite ends adapted to engage the teeth of said escape wheel, said pallet member oscillating about its pivot as said escape wheel rotates, a mass member, the interior of said pallet member being recessed to receive said mass member, said mass member being centrally pivoted about the same axis of oscillation as said pallet member, and spiral spring members interposed between said pallet member and said mass member on either side of said axis of oscillation for transmitting oscillatory force between said members.
JOHN G. M. VITI.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,918,378 Burnham July 18, 1933 2,069,082 Walle Jan. 26, 1937 2,362,836 McCullough Nov. 14, 1944 2,364,143 Horton et a1. Dec. 5, 1944 2,464,303 Gesellschap Mar. 15, 1949 FOREIGN PATENTS Number Country Date 11,032A Great Britain May 10, 1890 287,844 Germany Oct. 10, 1913 558,322 Great Britain Dec. 31, 1943